1. Field of the Invention
Embodiments of the present invention relate generally to magnetic heads, sliders, disk drives, and methods and, in specific embodiments, to a head comprising a substrate, a read structure for reading magnetic fields from a recording medium, an undercoat material for at least partially providing electrical insulation between the read structure and the substrate, and at least one of (i) a heating element located at least partially in the undercoat material for providing heat and (ii) a pedestal for at least partially providing thermal conduction between the read structure and the substrate.
2. Related Art
A major goal among many disk drive manufacturers is to continue to increase an amount of data that can be stored on a recording medium while still maintaining data integrity and disk drive reliability. Two ways that have been proposed for increasing a recording density in disk drives are: (i) lowering a flying height of a slider over a recording medium; and (ii) storing magnetization vertically within a recording medium, as in perpendicular recording, rather than storing magnetization longitudinally in the recording medium, as in longitudinal recording.
However, there have been problems with lowering a flying height of a slider in that damage may be caused due to contact between the slider and the recording medium. Also, there have been problems with perpendicular recording in that perpendicular disk drives are more sensitive to external stray magnetic fields than are longitudinal disk drives, and such external stray magnetic fields may lead to a loss of performance and even to irreversible disk drive failure in perpendicular disk drives.
A disk drive typically includes a slider and a recording medium. The slider typically includes a body section, a read structure, and a write structure. The read structure typically comprises a read element and two read shields, where the read element is located between the two read shields. The read element generally allows for reading data from the recording medium, and the two read shields generally allow for at least partially shielding the read element from stray magnetic fields. The write structure typically comprises a write pole, a write yoke, and a write return shield, where the write structure allows for writing data to the recording medium. The read structure and the write structure are generally located near a trailing edge of the slider. The slider is typically configured to fly on an air bearing that is generated by rotation of the recording medium.
Examples of disk drives are provided in the following references: (i) U.S. Pat. No. 6,760,191 entitled “Internal Heat Dissipater used to Reduce Slider and Write Pole Thermal Protrusion for Thin Film Recording Heads”, the contents of which are incorporated by reference herein; (ii) U.S. Pat. No. 6,842,313 entitled “Floating Down Stream Perpendicular Write Head Shield”, the contents of which are incorporated by reference herein; and (iii) U.S. Pat. No. 6,597,539 entitled “Suspension Assembly for Supporting a Read/Write Head over a Rotating Storage Disk with Dynamically Adjustable Fly Height”, the contents of which are incorporated by reference herein.
Increasing a magnetic storage density of a recording medium requires increasing a number of data bits per square inch on the recording medium. Placing a read structure and a write structure of a slider closer to a recording medium allows for increasing the magnetic storage density of the recording medium. This is because a magnetic field detected by a read element from a portion of the recording medium under the read element increases exponentially as the read element is moved closer to the recording medium. Moving the read element closer to the recording medium allows for compensating for lower flux levels provided from smaller areas on the recording medium where a given bit of data is recorded. Also, a strength of magnetic flux from the write structure to the recording medium and an accuracy of directing magnetic flux to a specific portion of the recording medium may be improved the closer the write structure is to the recording medium.
However, placing a slider closer to a recording medium may increase a probability that the slider will contact the recording medium when flying over the recording medium. Such contact between the slider and the recording medium may damage the slider and the recording medium. As a consequence, disk drive reliability may be adversely affected by contact between the slider and the recording medium due to low flying heights of the slider over the recording medium.
One proposal for increasing a magnetic storage density in a disk drive while limiting adverse consequences relating to disk drive reliability is to only position a slider close to a recording medium during read or write operations, and then to increase a distance between the slider and the recording medium during idle times when no read or write operations are being performed by the disk drive. This would allow for obtaining the benefits of lower flying heights during read and write operations to increase a recording density, while obtaining the benefits of higher flying heights during idle times to attempt to limit adverse consequences on disk drive reliability. However, there exists a need for flying height adjustment schemes that provide for greater efficiency and increased controllability.
With respect to perpendicular disk drives, experiments have demonstrated that perpendicular disk drives are sensitive to external stray magnetic fields that are generated by sources external to the disk drives. External stray magnetic fields may be generated by many external sources including, but not limited to, motors, magnets, electric currents, and the like. For example, external stray magnetic fields entering a particular disk drive may be caused by drive motors of adjacent disk drives that are in a same enclosure with the particular disk drive. Also, with disk drives placed in televisions, automobiles, computers, and the like, there are many potential sources of external stray magnetic fields, such as power supplies, motors, electric circuits, and the like.
In various experiments, a loss of performance has been observed in perpendicular disk drives when they are operated in the presence of external stray magnetic fields. Such a loss of performance was noticed even for relatively small external stray magnetic fields. For example, in various experiments, one order of bit error rate (BER) loss was observed in perpendicular disk drives when the disk drives were in the presence of external stray magnetic fields with strengths even as small as 10 Oersted (Oe). A possible explanation of the BER loss is an increase in asymmetry of a read element due to a resulting stray magnetic field in a vicinity of the read element.
Also, in various experiments, an irreversible disk drive failure has been observed if a perpendicular disk drive is operated in the presence of a large enough external stray magnetic field. For example, irreversible disk drive failures have been observed in perpendicular disk drives that are operated in the presence of external stray magnetic fields with strengths even as small as approximately 50 Oe. The irreversible failures of the disk drives have been associated with an erasure of servo data on recording media in the disk drives. Servo data on a recording medium permits the determination of the position of a head with respect to the recording medium, and if the servo data is erased, the head is not able to be positioned properly for read and write operations, which leads to an irreversible drive failure.
Based on the experiments that show a loss of performance and even a possible irreversible disk drive failure for relatively small external stray magnetic fields, it is important to try to determine a possible explanation for the increase in asymmetry of a read element and an erasure of data on a recording medium due to such relatively small external stray magnetic fields. It has been noted in U.S. Pat. No. 6,995,950 entitled “Transverse Biased Shields for Perpendicular Recording to Reduce Stray Field Sensitivity”, the contents of which are incorporated by reference herein, that read shields capture stray magnetic fields. In an analysis that has been performed, the read shields have been found to provide a large magnetic field when in the presence of an external stray magnetic field, which can explain the increase in asymmetry of a read element and the erasure of a recording medium.
Traditional read shields are manufactured with thicknesses that are designed to provide good domain structures such that the creation of bad magnetic domains in the read shields can be hopefully avoided. However, it has been determined that the geometries of traditional read shields cause the read shields to capture, focus, and greatly magnify external stray magnetic fields, which can lead to strong magnetic fields near a read element and a recording medium in a disk drive to possibly result in a loss of performance in the disk drive and an irreversible drive failure in the disk drive.
In light of the above-mentioned problems, there is a need for sliders that allow for improved flying height adjustment. There is also a need for sliders in disk drives that provide for reducing a magnification of external stray magnetic fields by read shields than with traditional sliders. Also, there is a need for sliders with features that allow for improved flying height adjustment while also providing for less magnification of external stray magnetic fields by read shields.